MaxSerial - MAX232 based serial board

I finished these off last night, and I must say, I'm very impressed with the reliability of the Max232 based connection; it is on par with the FTDI/USB connection on my [u]Diecimila board[/u] and [u]the iDuino/u. Gone is the questionable reliability of the transistor-based connection.

The boards are based off the Freeduino PTH layout and include all the usual Diecimila-style goodies like auto-reset and a (optional) 3.3V regulated output. Obviously the layout is compatible with shields.

The [u]directions have many more details[/u] including a BOM, assembly instructions, and board/schematic sources.

I'm pleased to be able to offer these as [u]kits[/u], [u]assembled[/u], and [u]bare pcbs[/u].

These are bourne out of being fed-up with transistor serial boards; so comments, questions, whatever...

Looks awesome. For most of my projects USB is more convenient, but if I ever want a serial connection I'll probably get one of these.

great board, any chance that this can be done a singe side board for home etching?

You may have better luck than me, but I couldn't fit the MAX232 and associated bits into the footprint of even the much larger SS-Serial board. Even double sided the board still has a few vias.

If you can fit it onto a reasonably sized single sided board, I'd love to hear, otherwise, I sell just the bare board for exactly this reason. If you'd like a starting point, the board/schematic are available at the end of the directions.

Your directions are very detailed, thanks! Do you know a cheap source for the MAX232 or equivalent? The RoHS compliant replacement for it is called MAX232CPE+ but costs ~ £25 here in the UK...

Your directions are very detailed, thanks! Do you know a cheap source for the MAX232 or equivalent? The RoHS compliant replacement for it is called MAX232CPE+ but costs ~ £25 here in the UK...

Maplin has it for £2.28

http://www.maplin.co.uk/search.aspx?MenuNo=12487&MenuName=RS232%2f233%2f422&worldid=-2&FromMenu=y&doy=search

or you can get the MAX232CN for £1 from here: http://www.cricklewoodelectronics.com/Cricklewood/product.php?productid=11938&cat=0&page=1

Your directions are very detailed, thanks! Do you know a cheap source for the MAX232 or equivalent? The RoHS compliant replacement for it is called MAX232CPE+ but costs ~ £25 here in the UK...

If your ordering a serial board anyway (or even if your not), I carry MAX232 clones (DS14C232CN) for 90¢ (about £0.45).

I just posted this one at http://www.freeduino.org/buy.html. If anyone has other Freeduino products they'd like to see on that page, drop me a line.

D

Hi

I am sorry ,but I didn`t understand why all grounded point leaved without any ground connection,should I add a ground plane to the board.

I maked freeduino v 1.2 and after that I noticed that grounded points has not any ground connection ,so I redesigned it,but want to know what was the designer porpuse to leave all grounded points lonely.

Ray

I see it is marked 5V and 9V . I dont have eagle to look Is this able to feed 9V into jumper marked so and is this put back through 5V reg first? How does power in work that way?

The “9V” pin is connected to the cathode of the power input protection diode. So it’s not exactly the same as connecting to the power jack, but you can use it to feed unregulated power to the 5V regulator input.

So it does feed to the 5Vregulator then . It is not feed 9V to the chip?

It is not feed 9V to the chip?

Its feeds 9V to the regulator chip. The MAX232 and ATMega CPU are powered by the regulated 5V.

So it does feed to the 5Vregulator then . It is not feed 9V to the chip?

It can be used two ways. If there is an extenal voltage source plugged into the external power connector, then the Vin pin can output that same external voltage (minus one diode voltage drop) and be used to power things that require the higher voltage avalible from an external power source, there is a 1 amp limit based on the series voltage polarity protection diode.

If there is nothing plugged into the external power connector then the Vin pin can be used to input a voltage that only goes to the input of the on board +5vdc voltage regulator.

Lefty

Hi

I am sorry ,but I didn`t understand why all grounded point leaved without any ground connection,should I add a ground plane to the board.

I maked freeduino v 1.2 and after that I noticed that grounded points has not any ground connection ,so I redesigned it,but want to know what was the designer porpuse to leave all grounded points lonely.

Ray

but want to know what was the designer porpuse to leave all grounded points lonely.

Probably to save money: the extra layer adds to the cost of making the board, and most Arduino buyers want low-cost boards.